Damaged aortic valve. Transoesophageal echo (TOE) ultrasound scan of the heart showing stenosis (narrowing) of the aortic valve (centre right). The most common cause of stenosis is the build up of fatty plaques (atherosclerosis). Symptoms include breathlessness, angina (heart pain) and heart enlargement. There are four valves in the human heart, all of which prevent the backflow of blood. Damage to the valves can lead to malfunctioning of the heart and death. If a damaged valve cannot be repaired it must be replaced.